Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$92.91	13.663%	$105.6043	$105.60	$105.60	$105.60
Purchase #2	$164.76	3.638%	$170.754	$170.75	$170.75	$170.80
Purchase #3	$129.25	10.765%	$143.1638	$143.16	$143.15	$143.20
Purchase #4	$224.36	6.482%	$238.903	$238.90	$238.90	$238.90
Purchase #5	$87.78	12.521%	$98.7709	$98.77	$98.75	$98.80
Purchase #6	$210.85	9.626%	$231.1464	$231.15	$231.15	$231.10
Purchase #7	$92.29	12.560%	$103.8816	$103.88	$103.90	$103.90
7 purchase totals =	$1,002.20		$1,092.2240	$1,092.21	$1,092.20	$1,092.30